Blagoi Marinov

Ventilatory efficiency and rate of perceived exertion in obese and non‐obese children performing standardized exercise

Sixty children, in the age span 6–17 years originally divided into two groups, matched by age, sex and height – 30 obese subjects [15 girls/15 boys; body mass index (BMI)=27·4 ± 4·5 m kg−2; ideal body weight (IBW) range=122–185%] and 30 controls (BMI=18·8 ± 2·7 m kg−2) performed incremental treadmill exercise test. Perceived exertion was assessed by means of Category‐Ratio Borg scale. The duration of the exercise for the children in the obesity group was significantly shorter than controls (P=0·010) but obese children have greater absolute values for oxygen uptake (VO2peak ml min−1=1907 ± 671 versus 1495 ± 562; P=0·013) and ventilatory variables (VE, VT), which adjusted for body mass decrease significantly (VO2/kg ml min−1 kg−1=29·2 ± 3·8 versus 33·6 ± 3·5; P<0·001). Among the various methods for ‘normalizing’ absolute values of VO2peak for body size, dividing it by body surface area (BSA) yielded the best results (VO2/BSA ml min−1 m−2=43·5 ± 4·6 versus 44·7 ± 5·6; P=0·335). The ventilatory efficiency determined either as a slope of VE versus VCO2 or as a simple ratio at anaerobic threshold did not differ between obese and non‐obese children in the incremental and recovery periods of exercise. There was a negative correlation of VE/VCO2 slope with age and anthropometric parameters. Obese children rated perceived exertion significantly higher than controls despite the standard workload (Borg score=6·2 ± 1·2 versus 5·2 ± 1·1; P=0·001). In conclusion, the absolute metabolic cost of exercise is higher in the obesity group compared with the control subjects. Both groups have similar ventilatory efficiency but an increased awareness of fatigue that furthermore limits their physical capacity.

University of Cincinnati Dyspnea Questionnaire for Evaluation of Dyspnoea during physical and speech activities in patients with chronic obstructive pulmonary disease: a validation analysis

University of Cincinnati Dyspnea Questionnaire (UCDQ) was developed to measure the impact of dyspnoea during (1) physical activity (Phys), (2) speech activity (Speech) and (3) simultaneous speech and physical activity (Comb). The aim of this study was to evaluate the validity of UCDQ in COPD patients, comparing it to a large set of dyspnoeic indices and functional parameters. Fifty COPD patients (age 58·7 ± 9·1 years, FEV1%pred = 39·3 ± 17·0%, Baseline Dyspnoea Index (BDI) = 4·9 ± 2·5, Six Minute Walk Distance (6MWD) = 373 ± 128 m, Symptoms score = 9·4 ± 2·5; mean ± SD) participated in the study. We found the following mean scores for the three sections of the questionnaire: Phys = 3·5 ± 0·9; Speech = 2·4 ± 1·1; Comb = 4·2 ± 1·0, meaning that patients report the most breathlessness during the combination of speaking and physical activity and the least breathlessness during speech activities. All three section of UCDQ had significant strong correlation with dyspnoea indices (BDI, Borg, MRC, OCD), 6MWD and symptoms score, which proves its concurrent and construct validity. Differentiation of patients by speech section (=3<) discriminated them significantly with respect to all dyspnoeic indices, symptoms score and 6MWD. All three dimensions of UCDQ had high test–retest reliability – ICC between 0·76 and 0·93. Factor analysis yielded three interpretable factors, as all dyspnoeic indices, three sections of UCDQ, symptoms score and 6MWD were loaded on the first factor. In conclusion, UCDQ provides valid and reliable information about the effect of dyspnoea on speech and daily activities.

Effect of Moderate and High-Dose Simvastatin on Asymmetric Dimethylarginine-Homocysteine Metabolic Pathways in Patients with Newly Detected Severe Hypercholesterolemia

The assumption that statin therapy can decrease asymmetric dimethylarginine through lowering low-density lipoprotein cholesterol levels seems logical and yet arises some controversy. The aim of the present study is to compare the effects of moderate (40 mg) to high (80 mg) simvastatin doses on asymmetric dimethylarginine and total homocysteine levels in patients with newly detected severe hypercholesterolemia (after target LDL-C levels, ≤2.6 mmol/L, are reached). The study included 120 adult patients with newly detected severe hypercholesterolemia (total cholesterol ≥7.5 mmol/L and low-density lipoprotein cholesterol ≥4.9 mmol/L). Asymmetric dimethylarginine levels were determined by enzyme-linked immunosorbent assay, total homocysteine-by a high-performance liquid chromatographic method. There was a statistically significant decrease in total cholesterol, triglycerides, low-density lipoprotein cholesterol, and apolipoprotein-B levels as well as in the apolipoprotein-B/apolipoprotein-A1 index after a 1-month therapy with 40 mg simvastatin (P <0.001). Asymmetric dimethylarginine and total homocysteine levels were also decreased but the difference did not reach statistical significance (P= 0.571; P= 0.569). A dose-dependent effect was established, comparing the influence of moderate (40 mg) to high (80 mg) simvastatin doses on the tested atherogenic biomarkers (lipid profile, apolipoprotein-A1, and apolipoprotein-B). Asymmetric dimethylarginine and total homocysteine levels were lowered significantly with 80 mg simvastatin (P <0.001; P= 0.038). In conclusion, optimizing the target values of low-density lipoprotein cholesterol, a moderate dose (40 mg) of simvastatin has no effect on asymmetric dimethylarginine and total homocysteine in contrast to a high dose (80 mg) after target LDL-C levels are reached (≤2.6 mmol/L) in patients with newly detected severe hypercholesterolemia.

Striving for Better Medical Education: the Simulation Approach.

Abstract Medical simulation is a rapidly expanding area within medical education due to advances in technology, significant reduction in training hours and increased procedural complexity. Simulation training aims to enhance patient safety through improved technical competency and eliminating human factors in a risk free environment. It is particularly applicable to a practical, procedure-orientated specialties. Simulation can be useful for novice trainees, experienced clinicians (e.g. for revalidation) and team building. It has become a cornerstone in the delivery of medical education, being a paradigm shift in how doctors are educated and trained. Simulation must take a proactive position in the development of metric-based simulation curriculum, adoption of proficiency benchmarking definitions, and should not depend on the simulation platforms used. Conversely, ingraining of poor practice may occur in the absence of adequate supervision, and equipment malfunction during the simulation can break the immersion and disrupt any learning that has occurred. Despite the presence of high technology, there is a substantial learning curve for both learners and facilitators. The technology of simulation continues to advance, offering devices capable of improved fidelity in virtual reality simulation, more sophisticated procedural practice and advanced patient simulators. Simulation-based training has also brought about paradigm shifts in the medical and surgical education arenas and ensured that the scope and impact of simulation will continue to broaden.

Evaluation of Acute Exogenous Hypoxia Impact on the Fraction of Exhaled Nitric Oxide in Healthy Males

Abstract Introduction: Exogenous hypoxia increases ventilation and contracts the pulmonary vessels. Whether those factors change the values of nitric oxide in exhaled air has not yet been evaluated. Objective: To examine the effect of exogenous normobaric hypoxia on the values of the fraction of nitric oxide in exhaled breath (FeNO). Subjects аnd Methods: Twenty healthy non-smoker males at mean age of 25.4 (SD = 3.7) were tested. The basal FeNO values were compared with those at 7 min. and 15 min. after introducing into the hypoxic environment (hypoxic tent), imitating atmospheric air with oxygen concentration corresponding to 3200 m above sea level. Exhaled breath temperature was measured at baseline and at 10-12 min. of the hypoxic exposition. Heart rate and oxygen saturation were registered by pulse-oximetry. Results: All the subjects had FeNO values in the reference range. The mean baseline value was 14.0 ± 3.2 ppb, and in hypoxic conditions - 15.5 ± 3.8 ppb (7 min.) and 15.3 ± 3.6 ppb (15 min.), respectively, as the elevation is statistically significant (p = 0.011 and p = 0.008). The values of exhaled breath temperature were 33.79 ± 1.55°С and 33.87 ± 1.83°С (p = 0.70) at baseline and in hypoxic conditions, respectively. Baseline oxygen saturation in all subjects was higher than that, measured in hypoxia (96.93 ± 1.29% vs. 94.27 ± 2.53%; p < 0.001). Conclusions: Exogenous hypoxia leads to an increase of FeNO values, but does not affect the exhaled breath temperature.

Effects of Acute Hypoxic Provocation on Autonomic Nervous System in Young “Healthy” Smokers Measured by Heart Rate Variability

Background and objectives: Smoking leads to autonomic dysfunction. However, the clinical methods for diagnosing this dysfunction are not sufficient. Since exogenous hypoxia leads to changes in the autonomic cardiac control, the aim of our study was to compare the activity of the autonomic nervous system via heart rate variability (HRV) in young “healthy” smokers and non-smokers before, during and after a short-term exogenous hypoxic exposure. Methods: Twenty-one healthy non-smoking males aged 28.0±7.4 (mean±SD) and fourteen healthy smoking males aged 28.1±4.3 with 9.2±5.6 pack-years were subjected to one-hour hypoxic exposure (FiО2=12.3±1.5%) via hypoxicator (AltiPro 8850 Summit+, Altitude Tech, Canada) with simultaneous recording of electrocardiography and pulse oximetry. HRV data was derived via specific software (Kubios HRV, Finland) by analyzing the pre-hypoxic, hypoxic and post-hypoxic periods. Results: Standard deviation of the intervals between normal beats (SDNN) was higher in non-smokers in the pre-hypoxic period (62.0±32.1 vs 40.3±16.2, p=0.013) but not in hypoxia (75.7±34.8 vs 57.9±18.3, p=0.167). When comparing intragroup HRV changes of shifting from hypoxic to post-hypoxic (normoxic) conditions we found that there is a significant increase in the root mean square of successive RR interval differences (RMSSD) (65.9±40.2 vs 75.1±45.9, p=0.011) and in the high frequency (lnHF) (6.8±1.4 vs 7.2±1.3, p=0.014) and a decrease in LF/HF (3.0±2.3 vs 1.9±1.5, p<0.001), but these changes were observed only in the group of non-smokers. Conclusions: Smoking likely impairs autonomic regulation in young healthy males and may lead to a decreased HRV even before subjective clinical signs and symptoms. Hypoxic exposure test could be Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 20 June 2018 doi:10.20944/preprints201806.0325.v1

LATE-BREAKING ABSTRACT: CAT for evaluation of recovery after severe exacerbation of COPD

Purpose: To determine the dynamics in CAT, pulmonary function and inflammatory markers during severe exacerbation of COPD in frequent and non-frequent exacerbators. Methods and materials: We evaluated 60 hospitalized patients (mean age 66.6±8.7, FEV1%-49.0±17.7, MRC = 2.2±0.7) using CAT, PEF, CRP, fibrinogen on day 1, 7, 30. Results: The mean CAT score on day 1, 7 and 30 is 23.8±8.5, 15.4±6.5 and 18.8±6.6. The mean values for PEF (L/min ) are 205.8±62.6, 230.2±66.8 and 228.2±63.3, for CPR (mg/l) 12.9±24.0, 6.6±6.6 and 8.9±12.7, and for fibrinogen 3.3±1.0, 2.7±0.8 and 3.1±0.8. On day 7 CAT, CRP and fibrinogen are significantly reduced (-8.4±6.1; p=0.001), (-6.3±19.1 mg/L; p=0.013) and (-0.6±0.8 g/L; p=0.001), and PEF is significantly increased (+24.3±47.4 L/min; p=0.001). Compared to day 7, on day 30th the values for CAT, CRP and fibrinogen demonstrate a trend to increase while PEF remains the same. Frequent compared to non-frequent exacerbators demonstrate significantlly higher values of CAT on day 1 ( 26.7±7.3 vs 21.1±8.7, p=0.009), which is observed also on day 7 and 30. There are nostatistically significant differences in PEF, CRP and Fbg in both groups. Conclusion: CAT is a sensitive tool for evaluation of patient9s health status during COPD exacerbation and correlates with changes in pulmonary function and inflammatory markers. Frequent compared to non- frequent exacerbators have higher values of CAT during exacerbation.

Reference Values For Forced Expiration Parameters In Bulgarian Children And Adolescents Aged 7 To 18 Years

Abstract INTRODUCTION: A diagnosis of lung function impairment in childhood is highly dependent on the respective reference values. Population differences in the pulmonary function of children have been frequently reported. The AIM of this study was to derive normal spirometric reference values for Bulgarian children and adolescents and to compare these results with other data set including our own reference equations developed 20 years ago. MATERIAL AND METHODS: Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and parameters of maximum expiratory flow-volume curves were measured in 671 healthy Bulgarian school children (339 males and 332 females) aged 7-18 years. Multiple linear regression analysis was performed for each spirometric parameter against age, height, weight, chest circumferences and fat free mass in both sexes. RESULTS: Excluding ratios, all measured spirometric parameters increased nonlinearly with age and height, and were significantly higher in boys than girls in adolescence. Height (H) explained the maximum variance for spirometric parameters and the best-fit regression equation relating functional parameters and body height was a power function (Y = a.Hb). FVC and FEV1 showed close correlations with height (r2 between 0.85 and 0.92), whereas the coefficients of determination for the flows were less close (r2 from 0.85 for PEF to 0.67 for MEF25%; always higher in boys). CONCLUSIONS: The developed prediction equations can be used in clinical practice. In comparison with reference equations based on European or USA populations, regional reference values are biologically more suitable for the interpretation of spirometric data. РЕЗЮМЕ ВВЕДЕНИЕ: Диагностика поражений легочных функ- ций в детском возрасте во многом зависит от применяемых референтных уравнений. Часто наб- людаются различия в легочных функциях у детей различных популяций. ЦЕЛЬ: Вывести нормальные спирометрические референтные стоимости для болгарских детей и юношей и сравнить эти результаты с другими дан- ными, включительно и с референтными уравнениями авторов, выведенными 20 лет назад. МАТЕРИАЛ И МЕТОДЫ: Форсированная жизненная емкость (ФЖЕ), форсированный экспираторный объем (ФЭО1) и показатели максимальных экспира- торных дебит-объемных кривых измерены у здоровых болгарских школьников - 671 (339 мальчиков и 332 девочки) в возрасте от 7 до 18 лет. Множествен- ный регрессионный анализ исползован для каждого спирометрического показателя в зависимости от возраста, роста, массы тела, окружности груди и от активной массы тела и при обоих полах. РЕЗУЛЬТАТЫ: За исключением соотношений для всех остальных измеренных спирометрических по- казателей устанавливается нелинейное нарастание с возрастом и ростом, при чем в юношестве они сигнификантно более высокие у мальчиков. Рост лучше всего отражает вариабельность спирометрических показателей. Самое подходящее регрессионное уравнение имеет вид power функция (Y=a.Hb). ФЖЕ и ФЭО1 показывают сильнейшую корреляцию с ростом (r² между 0.85 и 0.92), в то время как коэффициенты, определяющие дебиты, показывают более слабую корреляцию (r² от 0.85 для пикового экспираторного дебита до 0.67 для минутного экспираторного дебита); они всегда более высокие у мальчиков. ЗАКЛЮЧЕНИЕ: Предложенные референтные уравне- ния подходящи для применения в клинической прак- тике. Сравнение с референтными уравнениями для других популяций показывает, что эти, полученные на основании местных референтных стоимостей, более подходящи в целях интерпретации спироме- трических данных.

Exercise recovery phase: unrecovered part of the recommendations

To the Editors: As the implications of cardiopulmonary exercise testing (CPET) are continually growing, Palange et al. 1 are to be congratulated for their paper entitled “Recommendations on use of exercise testing in clinical practice”. It has been long awaited, as extensive research in the area simply outdated previous European 2 and American guidelines 3. As Palange et al. 1 mentioned that assessment requires integrative interpretation of a “cluster of response variables”, it seemed surprising that no parameter describing the recovery period was discussed. We would like to highlight the recovery period as an integral part of CPET, which is important for the sufficiency of data 2 …